Take a deep breath, you did the right thing by not starting the car. That’s important. Putting the wrong fuel in doesn’t automatically mean disaster, especially if the engine wasn’t turned on. The safest option is to have the tank drained and flushed by professionals before driving again. Yes, it’s inconvenient and costs a bit, but it’s far cheaper than engine damage. It happens more often than people admit, so no judgement here. We’re human, and forecourts can be busy and distracting. The key is acting quickly and calmly, which you did.